1. Field of the Invention
The present invention generally relates to material handling systems and, more particularly, to inspection and maintenance of such systems, especially those adapted for article sorting such as mail handling systems.
2. Description of the Prior Art
At the present time, many manufacturing and service industries make extensive use of material handling machinery for transporting and/or sorting of large volumes of objects. An exemplary application of such machinery is that of sorting articles in accordance with a designated destination by delivery services such as the United States Postal Service. Such services usually provide for transportation of articles such as cards, letters, parcels and the like from a large number of deposit sites to centralized local sorting facilities where the articles are sorted in accordance with transportation routes to similar facilities where further sorting by delivery routes is performed near the ultimate destinations of the articles. Further sorting processes may be included to accommodate extensive deposit and delivery areas with increased efficiency even though a single sorting process may provide sorting into hundreds of groups.
To automate the sorting process, a conveyor arrangement is often employed in combination with an arrangement for removing an article from the conveyor at a selected location. One such system in widespread use involves a conveyor comprising an endless train of carts circulating on a closed track on which the carts are captive. Each cart is provided with a tiltable tray for carrying articles and discharging them to either side of the closed track at appropriate locations under dynamically configurable computer control.
In such systems, the number of groups or classes into which articles may be sorted is only limited by the length of the closed track which may be physically accommodated within a particular facility and the nominal width in the direction of the track of a discharge station. Track lengths generally range between three hundred sixty feet and two thousand feet although larger or smaller installations are possible. Discharge or sort locations are somewhat larger in size than the length of carts which are provided and the carts are generally sized in accordance with the largest articles to be accommodated.
For mail sorting, a cart length of about eighteen inches is usually adequate. Thus, roughly two discharge locations can potentially be provided for each four feet of track (one on each side of the track) although some potential discharge locations must be used for loading articles onto the carts and other potential discharge locations are lost to curves in the closed track. Thus, even the smaller installations can generally provide at least one hundred sort classes or groups and potentially many more if increased track length can be accommodated in a given facility.
For such systems to operate at acceptably high speeds and without damage to the articles, the entire arrangement is fabricated with high precision and must be frequently maintained to avoid malfunction. For example, the closed track is generally formed of modular multi-suspension units which have a number of components such as shifting rails, alignment rails, code readers and linear motors which require inspection on a quarterly or semi-annual basis. The modular multi-suspension units are closed at the bottom for safety reasons and require vacuuming nominally on a semi-annual basis depending on environmental conditions at each location.
To allow multiple use of the large area required for such installations as well as article transport from the discharge locations, the multi-suspension units of the closed track are generally suspended fifteen to thirty feet above workroom floor level which is densely populated with additional article processing equipment and associated personnel. This location is not alterable consistent with efficient operations and space usage even though it presents significant difficulties in accessibility of the track for maintenance activities. Accordingly, maintenance personnel must use lifting devices such as so-called scissors lifts and cherry pickers to perform maintenance operations. In extreme instances, scaffolding must be built or the maintenance technician must work in a safety harness (which is precluded by safety regulations in some facilities).
Current cleaning and inspection procedures also require that the sorter/conveyor system be shut down and a number of the carts (generally five to ten, approximately corresponding to one or two modular multi-suspension units of the track) removed from the track to expose the track interior for inspection, cleaning and/or other maintenance. This removal is usually performed at a maintenance platform constructed at the track level. The train of carts is then advanced until the opening in the train of carts exposes the specific region of the track scheduled for cleaning and/or inspection. Once maintenance operations are completed on that region of the track, the train of carts may be advanced to expose additional areas of the track. When scheduled operations are completed or the sorter must be returned to service, the carts are replaced and normal operation of the sorter/conveyor is resumed.
It can be understood that this invasive operation precludes normal operation of the sorter/conveyor and even installations with very short track lengths cannot have cleaning and inspections performed for the entirety of the track in any single maintenance time window. In general, current and proposed installations are intended to operate every day with only two to four hour maintenance windows available on low volume days. No maintenance window is available at all during high volume periods when the consequences of a malfunction would be especially severe. In general, it is also estimated to be likely that approximately one thousand labor hours per year (for sorters of average size) will be required for maintenance activities on each sorter.
Thus, it can be seen that the ability to schedule adequate time for maintenance activities during the course of a year is marginal, at best, and impossible on sorters having relatively long track lengths. Additionally, it should be appreciated that required repairs must be accommodated and may preclude scheduled maintenance operations. Such repairs cannot presently be scheduled except to the slight degree that inspection during maintenance periods may allow a small percentage of malfunctions to be forecast. Thus otherwise routine repairs are only possible after a failure has occurred and the use of the sorter has been lost; substantially engendering an emergency to return the sorter to service.
It is therefore an object of the present invention to provide a method and apparatus for performing cleaning and inspection operations during normal operations of a sorter/conveyor.
It is another object of the invention to provide a maintenance cart by which cleaning and inspection operations may be performed remotely.
It is a further object of the invention to provide for communication of information from the sorter apparatus to report operating condition of the sorter and to indicate an impending need for repair and the exact location thereof.
It is yet another object of the invention to provide a method and apparatus capable of performing inspection and cleaning operations in reduced time and increased safety for personnel.
In order to accomplish these and other objects of the invention, a maintenance system for a material handling system having a track and a plurality of similarly dimensioned material handling carts connected in a continuous train and a maintenance cart therefor are provided comprising a cart chassis similarly dimensioned to a chassis of a material handling cart, an inspection and illumination system including at least one camera, and an illumination source, a position locating system for identifying a location of the camera relative to the track, and a telemetry transmitter for transmitting a signal representing at least an indication of the location of the maintenance cart and, preferably an image from the camera.
In accordance with another aspect of the invention, a maintenance cart for a material handling system having a track and a plurality of similarly dimensioned material handling carts connected in a continuous train is provided comprising a chassis similarly dimensioned to a chassis of a material handling cart, and a track cleaning system for removing material from the track and carried by said chassis of the maintenance cart.